Carbon collector and commutator for electric machines and apparatus



P 1942- K. FILEICSCHMANN 7 2,297,464

CARBON COLLECTOR AND COMMUTATOR FOR ELECTRIC MACHINES AND APPARATUS Filed May 5, 1941 Patented Sept. 29, 1942 CARBON COLLECTOR AND COMDIUTATOR FOR ELECTRIC MACHINES AND APPA- 1 RATUS Kurt Fleischmann, Mannheim, Germany; vested in the Alien Property Custodian Application May 5, 194-1, Serial No. 391,999 In Germany March 27, 1939 6 Claims.

This invention relates to carbon collectors and commutators for electric machines and apparatus.

The use of known metal collectors in electric machines and apparatus frequently causes commutating troubles at higher stresses. As the electrio conditions for commutation can be made easier by increasing the resistance of the short circuit of the brushes, machines have been built in which between the winding and the commutator bars special resistances are interposed which exclusively serve for increasing the resistance in the short circuit of the brushes.

Frequently the commutator was built up of bars consisting entirely of carbon. As carbon has a considerably higher specific resistance than copper or metal alloys, the employment of carbon bars as contemplated by the invention has the eflfect of considerably increasing the resistance in the short circuit of the brushes without necessitating the enlargement of the dimen sions of the machines.

.According to the invention the resistance of.

the carbon bars may be increased by giving them a shape suited for this purpose, for instance by lengthening the path of the current inthe bars by providing slots therein, etc., or by reducing the sectional area of path through the provision of clearances in the bars. Both means enlarge the resistance in the path of the short circuit current of the brushes.

The invention is illustrated by way of example in the accompanying drawing, in which I Figure 1 is a total view of a commutator ready for use built up of bars according to the invention, and

bars.

In the general arrangement shown in Fig. 1 the commutator'drum is built up of the bars 11.

Figs. 2-15 are detail views of differently shaped- The brushes b are gliding on the bars, which, as

shown in Figs. 2, 3, 5 and 8, may possess clearances on their long sides, which extend thereprevent sparking of the brushes on passing this clearance. It is f ther possible longitudinally to divide the bars a d to provide clearance on the joint faces, as indicated in Figs. 4 and 7. In the bar shown in Fig. 6 channels or bores traverse through it in longitudinal direction. In every instance, the cross section available for the how of current from one end of the bar to the other, i. e., y

from the brush side to the lugside, is reduced and the resistance in the path of the short-cir cuit current of the brushes is increased.

In the construction shown in Fig. 9 the bar is provided with notches extending transversely to the longitudinal direction thereof, that is, transversely to the commutator axis. The notches are found either on both sides, as shown in Fig. 9, to provide for a correspondingly long path from one end of the bar to the other, or they are arranged on one side only, as indicated in Fig. 10, so as to reduce the cross section of the bars at a number of places.

Figs. 12-15 illustrate how the longitudinal section of the bars is weakened by bores orclear-' at a number of places in the path of the shortcircuit current of the brushes.

What is claimed is:

1. A commutator comprising a plurality of bars consisting entirely of carbon, said bars being in part deformed from their normal contour to increase their normal longitudinal resistance.

2. A commutator comprising a plurality of bars consisting entirely of carbon, said bars being deformed from their normal contour along the outside to reduce their cross section and increase their longitudinal resistance.

3. A commutator comprising a plurality of bars consisting entirely of carbon, said bars being deformed along their inside to reduce their cross section and increase their longitudinal resistance.

4. A commutator comprising a pluralityof bars consisting entirely of carbon, said bars having definite radial deformations extending in a direction parallel to the commutator axis, and limited open areas on the joint faces of the bars to increase their longitudinal resistance.

5. A commutator comprising a plurality of bars consisting entirely of carbon, said bars being notched alternately frbm the inside to the outside and from the outside to the inside transversely to the longitudinal direction thereof to increase their longitudinal resistance.

6. Commutator comprising a plurality of bars consisting entirely of carbon, said bars being slotted on one side transversely to the longitudinal direction thereof to increase their longitudinal resistance KURT LEISCIIMANN. 

